Embryos of good quality can be frozen for later use using a technique called embryo vitrification. This technique is not harmful for the embryos, and it allows for the embryos to be stored indefinitely.
In order for the vitrification procedure to be carried out successfully, it is necessary to use a kit with the adequate media and materials. The most widely used kit worldwide is Cryotop, owned by the brand Kitazato.
The first step of the vitrification process is to dehydrate the embryos and then replace their inner cells for cryoprotectants. To do this, the embryos are put in different liquid media with an increasing concentration of cryoprotectants.
Then, embryos are put in a support system, which in this case is a straw.